OPTICAL HEAD APPARATUS INCLUDING A WAVEGUIDE LAYER WITH CONCENTRIC OR SPIRAL PERIODIC STRUCTURE

摘要

PCT No. PCT/JP89/00796 Sec. 371 Date Apr. 4, 1991 Sec. 102(e) Date Apr. 4, 1991 PCT Filed Aug. 2, 1989 PCT Pub. No. WO90/01768 PCT Pub. Date Feb. 22, 1990.An optical head arranged in such a manner that light emitted from a semiconductor laser (8) is inputted and coupled in a waveguide layer (3C) by a grating coupler (4C) having a concentric or spiral structure formed by concavities and convexities so as to convert light into waveguide light (12C) passing toward to outer periphery in the layer, the waveguide light (12C) is shifted at the outermost peripheral portion of the waveguide layer (3C) to a waveguide layer (3B) so as to convert the waveguide light (12C) into waveguide light (12B), the waveguide light (12B) is radiated by a grating coupler (4B) having a concentric or spiral periodical structure, the concentrically polarized (or radially polarized) light (13) is converted into linearly polarized light (14) by a polarizing element (10B) so as to be converged on the reflection surface (16) of the optical disc, light reflected from the reflection surface (16) is again converted into concentrically polarized (or radially polarized) light (17A) and (17B) by the polarizing element (10B) so as to be inputted and coupled in waveguide layers (3A) and (3B) by a grating coupler (4A) and the grating coupler (4B), and then to be turned into waveguide light (18A) and (18B) each of which passes through the layer, and the waveguide light (18A) and (18B) is radiated at the end portions of the waveguide layers (3A) and (3B) so as to be respectively received by photo detectors (6A) and (6B) so that a control signal and a reproduction signal are obtained.